The most important:

"Il fu Mattia Pascal" (1904)

A historical novel reflecting the Sicily of the end of the 19th century and and the general bitterness at the loss of the ideals of the "Risorgimento" (the movement that led to the unification of Italy), suffers from Pirandello's dency to "discompose" rather than to "compose", so that individual episodes stand out at the expense of the work as a whole.

"Uno, nessuno e centomila" (1925-26)

is at once the most original and the most typicalof his novels. It is a surrealistic desription of the consequences of the hero's discovery that his wife (and sthers) see him with quite different eyes than he does himself. Its exploration of the reality of personality is of a type better known from his plays. It is the most arresting presentation of the typical Piandellian contrast between art, which is unchanging, and life, which is an inconstant flux.
Characters that have been rejected by their author materialise on stage, throbbing with a more intense vitality than the real actors, who, inevitably, distort their drama as they attempt its presentation.

Enrico IV (1922)

Where the theme is madress, which lies just under the skin of ordinary life, and is, perhaps, superior to ordinary life in its construction of a satisfying reality. The play finds dramatic strenght in its hero's choice of retirement into unreality in preference to life in the uncertain world.